Isoprenoids comprise the largest family of natural products, including numerous secondary compounds which play different functional roles in plants as hormones, photosynthetic pigments, electron carriers, and structural components of membranes. The fundamental unit in isoprenoid biosynthesis, isopentenyl diphosphate (IPP), is normally synthesized by the condensation of acetyl CoA through the mevalonate pathway. In many organisms including several bacteria, algae and plant plastids, IPP is synthesized by a mevalonate-independent pathway. The initial step in this pathway is the condensation of pyruvate and glyceraldehyde 3-phosphate to form 1-deoxy-D-xylulose 4-phosphate. In the committed step towards IPP formation 1-deoxy-D-xylulose 5-phosphate reductoisomerase catalyzes in a single step an intramolecular rearrangement and reduction of 1-deoxy-D-xylulose 4-phosphate to form 2-C-methyl-D-erythritol 4-phosphate.
The E. coli 1-deoxy-D-xylulose 5-phosphate reductoisomerase enzyme has only recently been identified. Comparison of the amino acid sequence of the E. coli 1-deoxy-D-xylulose 5-phosphate reductoisomerase with those of Bacillus subtilis, Haemophilus influenzae, Helicobacter pyroli, Mycobacterium tuberculosis and Synechocystis sp. PCC6803 showed that there is little conservation among these sequences (Takahashi et al. (1998) Proc. Natl. Acad. Sci. USA 95:9879–9884).